Tesselation

 A Tessellation or tiling of the plane is a collection of plane figures that fills the plane with no overlaps and no gaps

 A regular tesselation is a highly symmetric tessellation made up of congruent regular polygons. Only three regular tessellations exist: those made up of equilateral triangles, squares or hexagons

We see tesselations everywhere we go, whether they're man-made like buildings and structures, or natural like fruit and plant life.